The present invention relates to a double diaphragm leakproof sealing device for electric windscreen washer pumps which is applicable, in particular, to motor vehicles provided with equipment for cleaning the front and rear glazed surfaces.
It is well known that in motor vehicles provided with equipment for cleaning the said surfaces, such equipment is provided with an electric pump which is coupled to an auxiliary cleaning liquid reservoir and which may be operated at will by the vehicle user. Also known are double acting pumps, i.e. those which operate selectively, by rotating in one direction or the other to direct the liquid flow towards the front of the vehicle or towards the rear. In these cases, the user has available the corresponding control member to be able to select the surface(s) on which the cleaning liquid is to be sprayed and the corresponding operation of the wiper blades associated with said surfaces.
By such selection, the user may spray the cleaning liquid on the windscreen and, even, simultaneously on the headlamps or spray the cleaning liquid on the rear window of the vehicle.
The known double acting pups are provided with a device for directing the cleaning liquid which is aspirated from the auxiliary reservoir by the suction and discharge impeller mounted in such pumps towards one or the other of such surfaces. This directing depends precisely on the direction of rotation applied by the electric drive motor to the suction and discharge impeller.
The known directing devices essentially comprise, in general, a directing chamber housing a diaphragm acting as a sealing valve. The directing chamber is arranged close to the pumping chamber where the pump suction and discharge impeller is housed. Both the pumping and directing chambers are connected together by passages through which the cleaning liquid pumped by the said impeller flows alternately, depending on the direction of rotation of the suction and discharge impeller. The directing chamber is provided with passages for the delivery of the cleaning liquid. The ports of said inlet and outlet passages are located, for each of the directions of rotation of the impeller in respective opposite sides of the directing chamber such as to define a chamber. In the chamber there is housed, intermediate said ports, a diaphragm which, as said above, acts as a stop valve.
The diaphragm is highly resilient. It may be deflected depending on the pressure exerted by the cleaning liquid pumped by the suction and discharge impeller so that, depending on the direction of rotation of said impeller, it blocks one or the other of the ports of the cleaning liquid outlet passages. The cleaning liquid may flow freely through the remaining outlet port towards the corresponding points of use.
Exemplary of said directing devices is Spanish utility model no. 287,059 for "Double directing device for electric windshield washer pumps" which, further to the novel elements characterising it, comprises the operative members described in the foregoing paragraphs.
In general, the known embodiments of directing devices described suffer, as main drawback from the fact that their diaphragm occupies an intermediate position between the said cleaning liquid inlet and outlet passages. When not under pressure from the cleaning liquid, i.e., hen the impeller is not in operation, the diaphragm does not block either of the ports of the outlet passages or blocks only one of them, depending on the form it adopts after each use. Under these conditions, when the auxiliary cleaning liquid reservoir is at a higher level than the nozzles for spraying said liquid on the corresponding surfaces, the liquid flows freely and leaks out for a simple difference of head level, as happens for example, when transporting the vehicle from the works in a steeply inclined position.
Another operative drawback of the known directing devices is that during the early moments of operation of the suction and discharge impeller, the diaphragm is in an indeterminate position and does not produce an effective seal. Thereby the sealing of the corresponding discharge port is imperfect and a certain amount of liquid is discharged therethrough. This means that during the star up time of the pump some cleaning liquid is discharged over a surface or surfaces which the user had not selected for cleaning.